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May
1
comment Is it safe to derive two different keys with the same password and key derivation function using two different salts?
@fgrieu Agreed. This is crypto, so belt and braces (I am English) are often the default.
Apr
30
answered Is it fair to assume that SHA1 collisions won't occur on a set of <100k strings
Apr
30
awarded  Commentator
Apr
30
comment Is it safe to derive two different keys with the same password and key derivation function using two different salts?
In this situation I would tend to differentiate the keys by adding "-KEY1" and "-KEY2" to the initial master password before input to the KDF, YMMV.
Sep
24
awarded  Autobiographer
Sep
13
answered How hard to break a cipher if it has a different key for each word?
Apr
19
comment One time pad: why is it useless in practice?
Since the pad is at least the same size as the message, then if you have a secure channel to transmit the pad, you can often use the same channel to transmit the message itself, and not bother with the pad at all. OTPs are sometimes used when the pad transmission is simple (hand a memory stick to your spy) but the later message transmission is difficult (transmit the secret enemy plans).
Apr
15
comment Positioning of keys in encrypted text
Are you sure that you are not confusing the IV (Initialization Vector) with the key? It is common to prepend the IV to the cyphertext. It is an obvious error to prepend the key to the cyphertext.
Nov
30
awarded  Yearling
Nov
30
awarded  Yearling
Nov
28
awarded  Nice Answer
Nov
22
comment detecting ROT13/base64 encryption
@fgrieu: technically, ROT13 is a cypher, albeit a very weak one. It is a Caesar cypher with a key (=shift) of 13. The problem being that the key is not really a secret.
Oct
29
comment “Padless” One-time-Pad encryption
And if the "secret algorithm" is shorter than the message, then you no longer have a One Time Pad. If the "secret algorithm" is longer than the message, then why not use a plain OTP?
Oct
29
comment Crack SHA1 hash code
Brute force will do it. How long it takes depends on how many bits there are in the constant value.
Oct
9
comment How to encrypt a short string and keep the length secret
@Erik: I was giving the standard definition of bit padding, which is defined in terms of bits. My last sentence in that section, "In byte terms..." gives the byte version.
Oct
7
answered How to encrypt a short string and keep the length secret
Aug
25
answered Can I make a cipher (ex: Vigenère) harder to break?
Jun
5
comment Removing Padded Value in Decrypted Message
PKCS#7 padding can always be removed because the last byte of the padded message tells you how much padding there is. If your original message is 02 02 02 ... 02 02, and the padded message is 02 02 02 ... 02 02 02 02, then you know that the last two bytes, and only the last two bytes, are padding. The other bytes are the actual message.
Dec
31
answered Why not use an algorithm's code rather than data itself for one time pads?
Dec
16
answered How to choose a padding mode with AES